The Translate Toolkit is a set of tools designed to assist translators and localisers, with a specific focus on the Gettext PO and XLIFF formats. These tools currently include converters for Mozilla to PO and OpenOffice to PO, and checkers for punctuation, accelerators, etc.

Gaupol is an editor for text-based subtitle files. It supports multiple subtitle file formats and provides means of creating subtitles, editing text, and timing subtitles to match video. The user interface is designed with attention to batch processing of multiple documents and convenience of translating.

ccextractor is a tool that analyzes video files (DVDs, Transport Streams, Tivo, Media Center, and others) and produces independent subtitle files (.srt and .sami) from the closed captions data. It is portable, small, and very fast. It also supports H.264.

Google2SRT allows you to convert subtitles from
Google Video and YouTube to the SubRip (.srt)
format, which is recognized by most video players.
You can download XML subtitles or simply type the
video's URL, and Google2SRT will do the rest.

Aegisub is an advanced subtitle editor that assists in the creation of subtitles, translations, and complex overlays using audio or video. Developed by enthusiasts it builds on workflows created and perfected through professional, hobby, and everyday use.

sdvplayer is a tool to help you improve your vocabulary in a foreign language by watching movies with subtitles in that language. It allows you to look up the meaning of a word displayed in the subtitles just by clicking on it. The meaning will be printed right on the screen and the player will be paused. Playing can be resumed just by pressing the space bar. It can play movies in many of the formats supported by libav*. Subrip (.srt), microDVD, and subviewer subtitle formats are supported. The meaning can be looked up through an external command. The built-in dictionary parser can parse the stardict dictionary format.